For the purpose of obtaining a better monochromatic image or a gray scale by an ink jet recording method or the like, an ink set comprising two kinds or three kinds or more of black inks having different carbon black concentrations is used in some cases. As this kind of black ink, a black ink composition defining a carbon black concentration, and a solid matter concentration of a prescribed amount of a fine particle emulsion corresponding to the carbon black concentration is disclosed (JP-A-2004-225036, JP-A-2004-225037). Among such the black ink compositions, in a black ink composition having a low pigment concentration, a resin content is higher than that of a normal aqueous ink composition. According to these black ink compositions, phenomenon in which reflected light generated by reflection of a fluorescent lamp or natural light from an image recorded using a dilute black ink composition produces golden gloss, and phase shift in an image recorded using a black ink composition for intermediate gradation (phenomenon in which, by changing an observation angle of an observer relative to a recorded image printed on a recorded medium or by changing an irradiation angle of a light source, original lightness of gray is observed to be shifted to a black side or a white side, at a part of a recorded region) can be suppressed.
In addition, as an ink used in an ink jet printer or the like, an aqueous ink composition using a pigment is known, and a pigment is excellent in light resistance and water resistance as compared with a dye, and is utilized as a coloring agent of an ink which allows for the better color developed state for a longer period of time after recording. Since the pigment is generally insoluble in water, when the pigment is used in an ink, it is necessary to mix the pigment with a dispersant such as a resin, to stably disperse this in water. For stably dispersing the pigment in water, it is necessary to study a kind and a particle diameter of the pigment, a kind of a resin used, and a dispersing means, and many dispersing methods and ink compositions for ink jet recording have previously been proposed. JP-A-2000-1639 describes that the discharge stability and the film physical properties such as friction resistance can be improved using a polyurethane resin as an aqueous resin in an aqueous ink composition.